1. Field of the Invention
The present invention relates to a control unit that centralizes control by grouping a plurality of paths.
2. Description of the Related Art
FIG. 21 shows a system including a belt conveyer and a plurality of marking machines. This system includes a belt conveyer 10, a first marking machine 11, a second marking machine 12, and a control unit (not shown) that controls the belt conveyer 10, the first marking machine 11, and the second marking machine 12. This system performs marking at a predetermined position of a target object 20 conveyed by the belt conveyer 10 in a movement direction 21. The operation pace of the entire system depends on the pace of belt conveyer 10 and the marking machines 11 and 12 operate at an assigned timing.
When the entire system is controlled by one path and one sequence program, if the belt conveyer 10 is instructed to set the pace of the entire system to 50%, the marking machines 11 and 12 operate at a pace of 50%, thereby ensuring the operation timings of the belt conveyer 10 and the marking machines 11 and 12.
Japanese Patent Application Laid-Open No. 2004-86306 discloses a multipath numerical control unit that solely controls a machine tool for performing a plurality types of machining or machining and other types of work, such as turning, milling, loader control, and so on. As disclosed in Japanese Patent Application Laid-Open No. 2004-86306, when different types of control are performed concurrently, a method of dividing the system into a plurality of paths and operating the individual paths independently in parallel has been used. In addition, while the individual paths are independently operated normally, they are operated coordinately with each other as needed, thereby enhancing versatility of the system.
Since the entire system is controlled by one path in the system shown in FIG. 21, the independence of individual components is lost. In addition, if the system structure or machining instructions are changed even partially, the control of the entire sequence program needs to be changed, thereby expending much effort.
If the system is controlled by a plurality of paths and a plurality of sequence programs, the independence of the individual components is maintained. Accordingly, if the system structure or machining instructions are changed partially, the control of the necessary part only needs to be changed, thereby enabling flexible responses. However, since the system is controlled by a plurality of paths, if the belt conveyer is instructed to operate at a pace of 50%, the control needs to be changed so that the individual marking machines operate at a pace of 50% (that is, so that the plurality of sequence programs are coordinated/with each other), thereby expending much effort in constructing the system.
Although the sequence programs for controlling a plurality of paths need to be coordinated with each other to achieve cooperation between the plurality of paths as described above, the creation of the coordinated sequence programs is difficult. In addition, since the coordinated sequence programs need to be changed when the system structure is changed, a lot of time needs to be spent each time the system structure is changed.